https://seclists.org/oss-sec/2026/q3/1001: OpenSSL Security Advisory [29th September 2026]
Published Sep 29, 2026
·Updated
Affected Software
1 affected component
OpenSSL OpenSSL=4.0, =3.6, =3.5, =3.4, =3.0, =1.1.1, =1.0.2
Frequently Asked Questions
1
What conditions are required for the issue to occur?
A DTLS handshake message must be written in multiple fragments, and the write must suspend part-way through with WANT_WRITE because the underlying transport temporarily cannot accept more data. While that write is suspended, the DTLS retransmission timer must fire and retransmit an earlier message from the retransmission queue.
2
What could a remote peer observe or cause?
The peer can receive heap memory disclosed as plaintext handshake data when the retransmitted message is read past its message buffer. If the read reaches an unmapped memory region, the condition can instead crash the process and cause denial of service.